As is known, low-voltage circuit breakers (i.e., ones for applications with working voltages of up to 1000 V) are devices designed for the purpose of protecting correct functioning of specific parts of the electrical system in which they are inserted and of the loads corresponding to said electrical system. For example, they ensure the rated current required for the different loads, enable a correct insertion of the loads into, and detachment thereof from, the circuit and enable automatic breaking of the protected circuit via galvanic separation or opening of appropriate contacts in order to obtain total isolation of the load from the source of electrical energy in the event of faulty operation of a specific branch of the system. The device that enables the circuit breaker to recognize automatically the states of faulty operation and to intervene accordingly with opening of the circuit is referred to as protection unit.
The aforesaid automatic low-voltage circuit breakers exist in different types, such as, for example, the so-called moulded-case circuit breakers (MCCBs), and the so-called air circuit breakers (ACBs).
Automatic circuit breakers can normally be equipped with a wide range of additional accessories. Amongst the accessories with which a normal circuit breaker can be equipped, it is possible to mention, for instance, auxiliary contacts for signalling of state (which may be open, closed, or tripped), servo-actuators for opening, closing, and resetting (solenoid controls or motor controls, devices for loading springs), undervoltage relays, temperature sensors, and other similar devices, which, as will be seen, fall within the scope of the present invention.
One of the limits of the above circuit breakers of a known type is represented by the fact that the various accessories are managed and wired independently of one another. To be exact, in the known solutions, each of the accessories mounted in the automatic circuit breaker is equipped with a bus of its own, designed for the various functions of supply, control, or transmission of the signals corresponding thereto.
Clearly, in the above conditions, the circuit breaker is traversed in various ways by auxiliary cables of different types, which, from one case to another, may remain within the overall volume of the circuit breaker, or else terminate on the outside thereof, so as to give rise to the necessary operative connections with other parts of the system, such as for example external displays, push-buttons and electronic control units, interlocking systems, dialogue units or supervision units.
As is known, in an electrical system the presence of numerous auxiliary cables is always far from appreciated, for example because it subjects the system to greater risks of error in the steps of wiring and maintenance. Furthermore, all the auxiliary conductors must be technically adequate from the electrical, mechanical and thermal standpoints, and from the standpoint of electromagnetic compatibility. In addition, they must be readily identifiable, and this obviously entails a high general complexity of the system that inevitably implies heavy burdens.
In particular, in a normal wiring situation it is possible to find simultaneously different buses corresponding to the different accessories installed, such as for example for the actuator, the auxiliary contacts, the thermal sensors, and the warning units, and each of these is called upon to carry, independently and according to its own protocol, signal flows that may be variously used and treated both inside and outside the circuit breaker.
Another drawback linked to the excessive presence of auxiliary buses or cables consists in the need to guarantee for each of them an adequate protection from undesirable mechanical or thermal actions that may arise in time as a result of other components present inside the automatic circuit breaker or the electrical switchboard that houses it. The very presence of cables entails, in any case, the need to activate adequate maintenance cycles, the costs of which of course increase according to the complexity of the system.
The wiring methods of the known art moreover exploit important physical areas both within the circuit breaker and on the electrical switchboard that houses it, in contrast with the wiring principle of optimization and economy of space.
It is evident from what has been described above that there exists in the state of the art the need to have technical solutions that will represent a valid alternative to the known methods and devices of management and dialogue for accessories, warning displays and protection units for automatic circuit breakers, as well as devices for dialogue with an external supervising unit.